pymysql的使用（笔记）

最新推荐文章于 2025-04-22 10:05:26 发布

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这篇博客详细介绍了如何使用pymysql库进行Python数据库操作，包括连接MySQL数据库、执行查询、插入、更新和删除等操作。通过示例代码展示了不同操作的实现，适用于学习和参考数据库操作技巧。

pymysql的使用（笔记）

首先，连接数据库：

import pymysql

def conn_db():  # 连接数据库函数
    conn = pymysql.connect(
        host='localhost',
        user='root',
        passwd='root',
        db='swjtu_z16',
        charset='utf8mb4')
    cur = conn.cursor()
    return conn,cur

def exe_update(cur, sql):  # 更新语句，可执行update,insert语句
    sta = cur.execute(sql)
    return sta

# def exe_delete(cur, ids):  # 删除语句，可批量删除
#     for eachID in ids.split(' '):
#         sta = cur.execute('delete from cms where id =%d' % int(eachID))
#     return sta

def exe_query(cur, sql):  # 查询语句
    cur.execute(sql)
    return cur

def exe_commit(cur):
    cur.connection.commit()  # 执行commit操作，插入语句才能生效

def conn_close(conn, cur):  # 关闭所有连接
    cur.close()
    conn.close()

查询

# 调用连接数据库的函数
conn, cur = condb.conn_db()
sql_query = "select * from bridge_preprocessing_params"
params = defaultdict(str)

try:
    sta = condb.exe_query(cur,sql_query)
    results = sta.fetchall()
    for row in results:
        name = row[0]
        param1 = row[1]
        param2 = row[2]
        param3 = row[3]
        params[name] = (param1,param2,param3)
    condb.exe_commit(cur)
except Exception as e:
	print(e)
finally:
    condb.conn_close(conn, cur)

另一种写法（无封装）：（参考）

import pymysql  #导入 pymysql
 
#打开数据库连接
db= pymysql.connect(host="localhost",user="root",
 	password="123456",db="test",port=3307)
 
# 使用cursor()方法获取操作游标
cur = db.cursor()
 
#1.查询操作
# 编写sql 查询语句  user 对应我的表名
sql = "select * from user"
try:
	cur.execute(sql) 	#执行sql语句
 
	results = cur.fetchall()	#获取查询的所有记录
	print("id","name","password")
	#遍历结果
	for row in results :
		id = row[0]
		name = row[1]
		password = row[2]
		print(id,name,password)
except Exception as e:
	raise e
finally:
	db.close()	#关闭连接

插入（参考）

import pymysql
#2.插入操作
db= pymysql.connect(host="localhost",user="root",
 	password="123456",db="test",port=3307)
 
# 使用cursor()方法获取操作游标
cur = db.cursor()
 
sql_insert ="insert into user(id,username,password) values(4,'liu','1234')"
 
try:
	cur.execute(sql_insert)
	#提交
	db.commit()
except Exception as e:
	#错误回滚
	db.rollback() 
finally:
	db.close()

更新

def updateFunctions(denosing,outliers,standard):
    sql_update = "update bridge_preprocessing set denosing = '%s',outliers = '%s',standard = '%s' where id = '%s'"
    # 调用连接数据库的函数
    conn, cur = condb.conn_db()
    sta = condb.exe_update(cur, sql_update % (denosing, outliers, standard, "1"))
    condb.exe_commit(cur)
    condb.conn_close(conn, cur)
    return sta

另一种写法（无封装）：（参考）

import pymysql
#3.更新操作
db= pymysql.connect(host="localhost",user="root",
 	password="123456",db="test",port=3307)
 
# 使用cursor()方法获取操作游标
cur = db.cursor()
 
sql_update ="update user set username = '%s' where id = %d"
 
try:
	cur.execute(sql_update % ("xiongda",3))  #像sql语句传递参数
	#提交
	db.commit()
except Exception as e:
	#错误回滚
	db.rollback() 
finally:
	db.close()

删除

import pymysql
#4.删除操作
db= pymysql.connect(host="localhost",user="root",
 	password="123456",db="test",port=3307)
 
# 使用cursor()方法获取操作游标
cur = db.cursor()
 
sql_delete ="delete from user where id = %d"
 
try:
	cur.execute(sql_delete % (3))  #像sql语句传递参数
	#提交
	db.commit()
except Exception as e:
	#错误回滚
	db.rollback() 
finally:
	db.close()